L515 and T265 reference points

Where are the reference points of L515 and T265? Documentation is rather vague. T265 datasheet says that that "it pertains to the PCB inside chassis". What is that? PCB top, bottom, center? Which is top, which is bottom? L515 datasheet specifies depth but not the position of the reference point from which the distance is reported. Is it the center of IR camera? Or there is no center as the depth is reported as half the distance between IR emitter and the IR receiver? Could this be specified?